Florida Gov. Charlie Crist is getting the full Arlen Specter treatment as he struggles to hold on to Democratic support in his independent bid for the U.S. Senate.

The Florida Democratic Party is throwing money behind a crushing new ad that reminds Democrats and independents of Crist’s past as a partisan Republican, cutting together clips of the governor praising George W. Bush and Sarah Palin, talking up offshore drilling and calling himself “a Jeb Bush Republican.”

The clips of Crist come one by devastating one: “I’m about as conservative as you can get,” he says in the opening video. In another: “President Bush – he is a leader of courage and conviction.” In a third: “I was impressed at Gov. Palin being picked. I watched her speech today. I was very impressed.”

The commercial is running in select broadcast markets throughout Florida, including the politically pivotal I-4 corridor, according to a source familiar with the buy. The FDP ad comes days after a Mason-Dixon poll showed Crist’s support dropping to 28 percent, just five points ahead of Democratic Rep. Kendrick Meek and 12 points behind Republican frontrunner Marco Rubio.

Meek had a seven-point lead among Democrats, and the new spot’s closing frames won’t help Crist make up that gap. “I’m a pro-life, pro-gun, anti-tax Republican,” Crist says, insisting in the last clip: “I think it’s important for people to understand who the true conservative is in this race. And it's Charlie Crist.”

Crist has recently marshaled a handful of valuable Democratic endorsements in his effort to draw support away from Meek, picking up the backing of state Sen. Al Lawson and winning over former Rep. Robert Wexler at a weekend event in Boca Raton.

“There’s going to be one clear voice of sanity, one voice that says,’I’m going to do what’s right by the people of Florida,’” Wexler said, referring to Crist and acknowledging: “I know as a lifelong Democrat, I will most likely never do this again.”

The governor, who abandoned a Republican primary fight with Marco Rubio amid sagging poll numbers, has also gone on the air with his first negative ad – one that attacks both Meek and Rubio, now the GOP’s official nominee.

“Newspapers report the IRS is investigating Rubio,” the commercial charges. “Kendrick Meek steered government contracts to an indicted developer, who then hired Meek’s mother.”

But even as Crist has tacked left, raising the prospect that Democrats could embrace him as a stronger opponent for Rubio than Meek, the electoral math has gotten tougher. Democratic strategist Steve Schale, a Meek supporter who ran President Barack Obama’s 2008 campaign in Florida, estimated that Crist would have to win about a third of Democrats, a third of Republicans and half of the unaffiliated voters in order to claim victory.

“His only path to victory is to find a way to be Democratic enough to win enough Democrats, Republican enough to win enough Republicans, and to do that in a way where he doesn't anger Independents,” Schale wrote the week after Meek won the Democratic Senate primary. “Not exactly the easiest thing to do, when Democrats now have a plausible alternative in Meek and Republicans in Rubio.”